Transmitter with spiral-aperture disks



P 1939- K. SCHLESINGER 2,173,499

TRANSMITTER WITH SPIRAL APERTURE DISKS Filed Nov 28, 1936 J/IIen/or mvm.

Patented Sept. 19, 1939 UNITED STATES PATENT OFFICE TRANSMITTER WITH SPIRAL-APERTURE DISKS Steglitz, Germany Application November 28, 1936, Serial No. 113,192 In Germany December 2, 1935 1 Claim.

There have become known, inter alia from investigations by the applicant in his earlier patent applications Ser. Nos. 36,008 and 60,295 perforated disk scanning means, which employ for the particular purpose of the interlaced line method spiral-aperture disks having spirals comprising one or more turns. The picture to be scanned is generally a rectangle, but the scanning area of a scanning disk is a trapezoidal area. In order 1:) to correct this keystone distortion the applicant has arranged an optical device, i. e. a spheric lens, the plane of which is inclined against the picture plane, because in such an arrangement a rectangle projects as trapezium. It was found l? in the case of these investigations that the plane of the disk and the plane of the image equired to be disposed inclinedly in relation to one another in order to be able to utilise the effect of the collapsing lines for compensation of the division- 20 ing of the disk. In this connection the original image was assumed to be a rectangle, whilst the disk possesses at trapezoidal sectional area. In this connection, however, there unfortunately occurs a new error. This error consists in the :3 fact that equidistant lines on the object surface no longer appear equi-distant on the disk, since with an increase in the width, which leads to the trapezoidal form, there occurs simultaneously a variation in both dimensions, which leads to the 3H fact that the lines appear to crowd together towards the narrow end of the trapezium.

According to the invention to compensate the error of crowding together the lines at the one side, a disk is used having one or more spiral 35 turns the holes of which are arranged in such a manner that the fault of the optical distortion is eliminated. Such scanning disk has a spiral with a pitch increasing from one end to the other end of the spiral.

40 The novel feature which I believe to be characteristic for my invention are set forth with particularity in the appended claim. My invention, however, both as to its organization and method of operation together with further objects 45 and advantages thereof may be best understood by reference to the following description taken in connection with the accompanying drawing, in which.

Fig. 1 shows the optical arrangement, wherein the ray of light I proceeding from the light source 2 at first traverses the plane of the picture, for example a film 3, then that of a lens 4, and finally that of the multiple-spiral disk 5. It is neces- 5 sary to include in each case between the planes 3,

4 and 5 an angle on which is different to zero. In this way it is in fact possible to reproduce an original area, which is rectangular in the turned about position 3, in the form of a sectional area which is trapezoidal in the turned about position 5. In this connection, however, there unfortun ately occurs a new error.

The disk according to the invention with the aid of which the error may be removed is shown in Fig. 2.

An arithmetical spiral with two turns is represented therein by the curve 8a, 8b. In this the two pitches 8' and 8" are equal to one another. A disk of this kind is subject to the error of crowd- 2O ing together the lines at one end. In comparison there is shown as full line in the same figure the spiral according to the invention, which is no longer arithmetical and consists of the two turns 9a. and 9b. The turns 9 of the spiral according to the invention are always situated nearer to the central point than the turns 8 of the arithmetical spiral. As a result the pitch 9 of the inner spiral is smaller than the pitch 9" of the outer spiral. By this method of applying the points the stated error is compensated automatically. The extent of the correction depends on the optical data of the projection lens and the angle of inclination it etc., and may be readily calculated in each single case. p

KURT SCHLESINGER. 

